An international team of astronomers utilizing NASA’s Rossi X-Ray Timing Explorer (RXTE), believe that they’ve identified a candidate for the smallest known black hole. Using the RXTE, which detects X-rays coming from cosmic sources, the astronomers were able to identify a specific X-ray pattern – nicknamed a “heartbeat” – that indicates that a black hole is present in a binary system with the ordinary star. The “heartbeat” pattern is caused by the regular cycles of matter accumulated into the black hole from its neighboring star.
As the stellar matter (mostly gas) circles the event horizon of the black hole, its heated up to temperatures of millions of degrees, a process which causes X-rays to be emitted. The explusion of X-rays then temporarily pushes the gas away from the black hole, which is what causes the cyclical heartbeat-type pattern.
If the astronomers’ calculations are correct, this black hole is located about 16,000 to 56,000 light years away from Earth (a more precise distance hasn’t yet been determined). The black hole itself is only about three times the mass of the Sun, which means that the original star was just barely big enough to form a black hole. Our Sun, by contrast, lacks sufficient mass to form a black hole at the end of its life-cycle.
The astronomers plan to use this new data in conjunction with a similar X-ray pattern from another small black hole. As they continue to use that data and new data from the RXTE, they hope to learn more about smaller black holes and confirm that this X-ray heartbeat is really the sign of one.
by Alex Knapp taken from http://www.forbes.com/sites/alexknapp/2011/12/17/nasa-satellite-may-have-found-the-smallest-known-black-hole/